Using two rule files at the same time

[XakEp]

I was hoping someone could explain to me exactly what using -r twice in the same command with two different rule files does. Does it apply them at the same time or sequentially/separately to each guess?

example -

hashcat -m1000 -a0 -w4 -O -d 1,2,3,4 --hwmon-disable d:\pwdump.txt d:\wordlists\big\test.txt -r rules\dive.rule -r rules\hob064.rule